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Audio synthesizer experiment in C using aplay

//
// synth.c - audio synth experiment
// Author: Ted Burke
// Date: 13 Apr 2024
//
// To compile:
//   gcc synth.c -o synth -lm
//
// To run:
//   ./synth | aplay -f S16_LE -c1 -r44100
//

#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <math.h>
#include <unistd.h>

int main()
{
    int n, N;       // sample number, number of samples
    double f = 400; // fundamental harmonic freq
    double Fs = 44100; // sampling freq
    int16_t s;      // used to store one sample
    int16_t *buf;   // pointer to audio buffer

    // Allocate buffer to store audio samples
    N = Fs * 5;     // specify 5-second buffer
    buf = malloc(N * sizeof(s));
    if (!buf) return 1;

    // Generate waveform with several harmonics
    for (n = 0 ; n < N ; ++n)
    {
        s = 8000 * sin(2.0 * M_PI * f * n / Fs);
        s += 8000 * sin(2.0 * M_PI * 3*f * n / Fs);
        s += 8000 * sin(2.0 * M_PI * 5*f * n / Fs);
        s += 8000 * sin(2.0 * M_PI * 7*f * n / Fs);
        buf[n] = s;
    }

    // Write audio data to stdout
    fwrite(buf, sizeof(s), N, stdout);

    // Clean up and exit
    free(buf);
    return 0;
}